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Interplay between tolerance mechanisms to copper and acid stress in Escherichia coli.

Djoko, Karrera Y. and Phan, Minh-Duy and Peters, Kate M. and Walker, Mark J. and Schembri, Mark A. and McEwan, Alastair G. (2017) 'Interplay between tolerance mechanisms to copper and acid stress in Escherichia coli.', Proceedings of the National Academy of Sciences of the United States of America., 114 (26). pp. 6818-6823.


Copper (Cu) is a key antibacterial component of the host innate immune system and almost all bacterial species possess systems that defend against the toxic effects of excess Cu. The Cu tolerance system in Gram-negative bacteria is composed minimally of a Cu sensor (CueR) and a Cu export pump (CopA). The cueR and copA genes are encoded on the chromosome typically as a divergent but contiguous operon. In Escherichia coli, cueR and copA are separated by two additional genes, ybaS and ybaT, which confer glutamine (Gln)-dependent acid tolerance and contribute to the glutamate (Glu)-dependent acid resistance system in this organism. Here we show that Cu strongly inhibits growth of a ∆copA mutant strain in acidic cultures. We further demonstrate that Cu stress impairs the pathway for Glu biosynthesis via glutamate synthase, leading to decreased intracellular levels of Glu. Addition of exogenous Glu rescues the ∆copA mutant from Cu stress in acidic conditions. Gln is also protective but this relies on the activities of YbaS and YbaT. Notably, expression of both enzymes is up-regulated during Cu stress. These results demonstrate a link between Cu stress, acid stress, and Glu/Gln metabolism, establish a role for YbaS and YbaT in Cu tolerance, and suggest that subtle changes in core metabolic pathways may contribute to overcoming host-imposed copper toxicity.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Date accepted:23 May 2017
Date deposited:13 October 2017
Date of first online publication:13 June 2017
Date first made open access:13 December 2017

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